Packaging for pharmaceuticals and other medical implements typically employ multilayer films to provide adequate dust and moisture barriers for maintaining the integrity of the items contained within the packages. Conventional films used in these applications contain one or more polymers that are formed from halogenated molecules such as polyvinyl chloride (PVC), polyvinyldiene chloride (PVdC), or fluorinated-chlorinated resins such as poly-chloro-tri-fluoro-ethylene (PCTFE). Although films that incorporate these resins provide effective barriers, manufacturing and disposal of these films can result in undesired effects and sometimes dangerous byproducts. For example, dioxin can be formed from PVC production and disposal, and PVdC can cause excessive corrosion of equipment and packaging machinery.
Producing multilayer films and utilizing such films in a variety of packaging applications is well known. Multilayer films can be produced in a variety of ways and often include extrusion or co-extrusion steps followed by thermal or adhesive lamination, extrusion lamination, and/or extrusion coating. However, some films can be produced solely by co-extrusion.
Co-extrusion of multilayer films is well known in the art and includes co-extrusion blown films and cast films as described, for example, in U.S. Pat. Nos. 3,479,425, 3,797,987, 3,959,431, and 4,406,547. Multilayered films can be produced by co-extruding two or more melt streams through a die to produce a layered structure when allowed to cool. The co-extruded films can further be laminated to other film layers or can be coated with additional polymers to incorporate more layers into a final film product. Since not all polymers readily adhere to each other, some films may also incorporate tie or adhesive-containing layers that facilitate the adhesion of two or more layers in a film. These tie layers can be co-extruded with the other polymeric layers or can be introduced during a lamination process.
Packaging for pharmaceuticals or other moisture-sensitive materials requires not only low moisture permeability but also other properties such as chemical inertness, clarity, rigidity, or uniform thickness. Properties of the finished film such as overall thickness can be controlled by the relative speed and output of the individual extruders delivering the melt streams to the die. In addition, polymer viscosity and melting temperatures of the individual polymers can affect the thickness and adhesion of the layers to each other following extrusion. However, many of the desired finished film properties are unique to each layer within the multilayer film and, therefore, can make co-extrusion of certain films very challenging.
Multilayer films can be shaped into packaging by subjecting them to a thermoforming process. Plastic thermoforming processes are well known in the art and are described, for example, in U.S. Pat. Nos. 4,421,721, 4,994,229, 5,106,567, and 6,086,600. Generally, thermoforming is a process for forming a plastic container or packaging structure by heating a sheet of plastic film to a desired forming temperature and shaping the film by subjecting it to vacuum or pressure shaping in a mold.
Thermoformed blister packaging is often used for commercial packaging of food products, personal care products, and human health products such as pharmaceuticals and medical devices or other implements. The use of this type of packaging has become widespread mainly due to the ability to incorporate suitable moisture, dust, UV and/or gas barriers into the packages when such properties are desired for maintaining the product contained by the package. For example, pharmaceutical blister packaging is effective for maintaining drug tablet integrity. However, the common packaging today typically contains the undesired halogenated polymers described above.
Therefore, there is still a need for multilayer films and thermoformed packaging, especially for pharmaceuticals, that is free of halogenated polymers, is chemically inert and non-corrosive, is aesthetically pleasing enough to present the products contained therein, is durable enough to protect the packaging contents, and is capable of being manufactured on existing equipment in pharmaceutical fill/finish manufacturing plants.